Non-Radiographic Axial SpA: A Women's Disease?

Symptoms similar in non-radiographic and radiographic axial spondyloarthritis.

Patients with non-radiographic axial spondyloarthritis (AxSpA) bear a burden of illness similar to that of patients with radiographic disease.

Furthermore, these patients are more likely to be female, have a shorter disease duration, and show less objective inflammation as measured by C-reactive protein (CRP) and spinal inflammation on MRI scans, according to Dutch-German-French researchers, who published the finding online on in Seminars in Arthritis and Rheumatism.

Led by Annelies Boonen, MD, PHD, a rheumatologist at Maastricht University Medical Centre in the Netherlands, the study reviewed the epidemiology of non-radiographic AxSpA -- a relatively new categorization -- its effects on patient function and health-related quality of life (HR-QoL), as well as its potential effects on healthcare costs and workplace productivity.

Through a PubMed search of key words, the investigators evaluated almost 60 English-language original articles and reviews published from July 2003 to July 2013. However, the authors cautioned, "This review does not follow the methods of a systematic literature review and therefore does not include a formal assessment or analysis of bias risk."

Patient populations, geographical risk factors, and eligibility criteria varied widely among the studies, as did epidemiological estimates of SpA. In eight European studies SpA prevalence ranged from 0.3% in France to 1.7% in Germany. According to the U.S. National Health and Nutrition Examination Survey, 2009-2010, the national prevalence of SpA was 0.9% and 1.4% according to, respectively, the Amor classification criteria and those of the European Spondyloarthropathy Study Group.

One study found that if pain duration was no more than 1 year at time of referral, 67% of patients had non-radiographic and 33% had radiographic AxSpA. In those with 1 to 3 years of pain, the two categories were nearly equal at 53% and 46%, respectively. In those, however, with 6 to 9 years of pain, radiographic AxSpA was more likely to be present: 61% versus 39%.

Studies to date indicate that over 2 years about 10% of patients with non-radiographic AxSpA will progress to radiographic disease, with symptom severity and disease duration predicting progression.

Some studies showed a significant difference in the male-to-female ratio. In radiographic AxSpA males outnumbered females by about 2:1, whereas this ratio was reversed in non-radiographic disease. "These findings suggest that males may develop radiographic structural changes sooner or more frequently than females," the authors wrote.

Across the studies examined, similar high clinical disease activity as measured by the Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) was reported, regardless of radiographic status. In one cohort nearly 50% of non-radiographic AxSpA patients had a BASDAI score of at least 4. In other cohorts, pain, disease activity, and clinical impairment were similar in both groups.

Non-radiographic AxSpA patients, however, had significantly less inflammation (CRP levels), less spinal inflammation, and less extensive inflammatory lesions on MRI. One cohort subanalysis, however, found no significant difference in lesion between the two categories.

Radiographic AxSpA has been shown to have a substantial adverse impact on physical functioning, and some studies suggest that non-radiographic disease imposes similar limitations. In one cohort, about one-third of non-radiographic patients had a Bath Ankylosing Spondylitis Functional Index score of greater than 3, with similar scores emerging from other studies.

Non-radiographic AxSpA also has a similar impact on HR-QoL. In one cohort the proportion of patients with scores of at least 40 (better health) were not statistically different in the two groups as measured by the Medical Outcomes Short Form Questionnaire, both physical and mental components. In the same cohort, the Ankylosing Spondylitis Quality of Life (ASQoL) instrument found no significant variance in the proportions of AxSpA patients in both groups who scored at least 43% versus 50%, respectively, or in median levels of ASQoL (4.0 versus 5.5).

To date, there is little available data on economic outcomes in non-radiographic AxSpA disease, but its radiographic form is known to entail high direct healthcare and loss of productivity, including workplace absenteeism and withdrawal from the workforce. In the Netherlands, work disability among radiographic AxSpA patients was reported to be three times higher than in the general population, and in Argentina these patients were reported six times more likely to be unemployed. With less structural damage but similar pain levels and clinical and functional impairment, it is probable that non-radiographic AxSpA imposes a similar economic burden.

"Because the definition of non-radiographic AxSpA is still relatively new, additional studies are needed to answer outstanding questions about treated and untreated course of disease and its impact on outcomes, including work participation," the authors concluded.

Editorial and medical-writing support for his study was funded by Pfizer. The authors received no financial support for this research.

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